The G5 is loaded, packed to the gills with features, with the exception of wireless - being a gaming mouse, wired is standard. The G5 is a laser mouse, and while its maximum DPI resolution is not as high as some other laser mice, it is more than sufficient for anyone lacking the ability to score a head-shot within a tenth of a second of an enemy coming in view. In fact, its sensitivity is such that it may in some cases feel too sensitive, in which case the G5 accommodates you with a button that provides three different settings for sensitivity.
And then, of course, there are the weights. If I recall correctly, the G5 was one of the first gaming mice to incorporate the feature. Although the idea of adding weights to your mouse in order to adjust its weight may, at first glance, seem like an option only the most OCD of geeks could appreciate, it is actually a practical feature which I think more mice should use. Laser mice are highly sensitive, and as a result, they will pick up on little movements that older mice would not notice. This is a good thing when twitch-gaming, but its a bad thing if your room is cold and you've got the shivers, or if your desk isn't the most stable piece of furniture in the world. Adding weight makes the mouse feel less twitchy. If you're an average user, then you'll probably want to dump at least half of the available weights into the G5. The G5, with no weights added, seems eager to evade gravity, and as a result your cursor will move halfway across your screen every time a butterfly on the far side of the planet flaps its wings.
The only area where one might say the G5 is lacking is buttons. Left, right, two thumb buttons, and a click-able scroll wheel. The sensitivity buttons can potentially be re-mapped for use in games, but their location isn't terribly useful. So, five buttons, really - That's all folks, nothing more to see here. To be fair, that's all that you really need, and it isn't entirely reasonable to expect more from the G5 which, despite its gaming mouse credentials, is priced at the entry level for this kind of hardware. It is fair to expect them to be easy to use - and here the G5 stumbles, as its scroll button is a bit stiffer than it should be. It is easier to use then the notoriously difficult scroll button on the MX400, but it is far from perfect.